Electromagnetically-actuated displays generate a desired digit character or pattern by selectively positioning individual elements of the display to visible or non-visible orientations. The positioning mechanism is the inertreaction of a magnet with a magnetic field created when a drive coil is energized. A minimum current is required to position the element and a drive circuit must provide that minimum over the range of operating voltage and changes in drive coil resistance due to temperature variations. Normally such drive circuits provide the minimum current under the worst conditions, but much higher currents under normal or more favorable conditions. The resulting waste of energy is undesirable when operating from batteries and/or from expensive solar cells, etc. Thus for those and similar applications it is desirable to control the drive currents in an efficient manner.
The characteristics of this invention are that it controls these drive coil currents to the required level and excess available drive voltage is efficiently utilized through a current transformation in that average coil currents are greater than the average current into the drive circuit.